There is no safe level of lead for humans or in the environment. That's why lawmakers and scientists have worked to bar the heavy metal from gasoline, paint, cookware and toys.

Now it's time for Gov. Jerry Brown to sign a measure passed by the Legislature that would ban lead from bullets, which spew the metal into California's outdoors and the wildlife food chain.

Several gun and hunting groups aren't convinced, despite a world of scientific advice about the damage that spent bullets and fragments cause. These organizations, including the National Rifle Association, cite cost and convenience, problems that can be minimized as the proposed ban kicks in over a four-year period beginning in 2015.

Lead ammunition is already on the way out. Steel pellets replaced lead birdshot after federal wildlife authorities ordered the changeover in waterfowl hunting in 1991. In California, 14 counties along the Central and South Coast were put off-limits for lead ammo in 2008 to protect the scarce condor, a giant scavenging bird that picked up lead contamination from its diet of carrion shot by hunters. Portions of 35 other states also limit lead bullets in sensitive wildlife refuges.

There's a clear pattern here, and California would be wise to heed it. Lead - whether it comes out of a rifle barrel or gas nozzle - doesn't belong in the air, soil or water. It stunts growth, inflicts brain damage and causes death in humans, and harms wildlife.

Allowing continued use of lead ammo makes even less sense because there are options available to hunters. Cartridges using copper, steel and other metals are already on the market. The supplies should surge if California sets a new standard banning lead for its 274,000 hunters.

Opponents aren't sold, but it's unlikely anything would convince die-hard foes. The measure is decried as an attempt to ban hunting, a criticism that makes no sense when non-lead bullets are available.

These critics also dispute the harm to condors and other scavengers, though there's overwhelming evidence that lead levels in the birds have dropped since the metal was banned in their ranges.

The measure, AB711 by Assemblyman Anthony Rendon, a Democrat from Lynwood in Los Angeles County, comes with political quirks. Several labor groups that are loyal allies of Brown's oppose the measure, saying passage will impose a financial burden on their blue-collar hunter members. But other Brown loyalists, including different unions, along with environmental and animal protection organizations, favor the measure as a way to clean up the outdoors.

Brown, who says he's a gun owner, hasn't hinted at his outlook. He should consider the issues fully, weighing the changes it imposes on hunters against the documented hazards of firing more lead into California's backcountry.